This invention relates generally to apparatus and methods for remotely testing electrical circuits and more particularly, but not by way of limitation, to apparatus and methods for controlling from a remote location the testing of special service or private line telephone circuits passing through a common local location.
The need to test electrical circuits, particularly leased special service telephone circuits, has been recognized for many years. With regard to such leased telephone circuits, for example, testing a circuit line to determine the physical location where a problem exists saves money because maintenance personnel can then be more efficiently utilized. By remotely conducting such tests from a common test location, problems can be more quickly solved for better satisfying users of such leased private line telephone services.
One system which has been used to test special service/private line circuits utilizes test boards to which each testable circuit is physically, manually connectible to other circuits or test equipment by plugs and jacks. This technique has the shortcoming of requiring a large space where the test jacks and the hard wiring from the circuits can be maintained.
Automated or mechanized systems have also been developed and used in remotely testing telephone circuits. Many of these systems are large so that they can handle large portions of the telephone network. Some systems are somewhat smaller. However, one feature common to each of these test systems known to us is their requirement for a central computer to control the testing. The need for such a central computer makes these systems relatively expensive and necessitates that adequate communication links be established between the computer and the test equipment of the particular system. That is, where a central computer is used, it is located at a single location so that the operator needs to work from that location or otherwise arrange for multiple communication with both the central computer and the test circuitry.
These systems known to us also require relatively high quality conditioned communication links to handle the synchronous data transmissions where communications are between digital machines and where information is digitally transmitted to visual displays such as cathode ray tube terminals and/or hard copy printers. All of the described prior systems require the use of modems. Communications from these systems are in ASCII or FSK format; none are by synthesized speech verbally communicating the test results.
Another shortcoming of these systems is that many, if not all, are too costly for small-scale applications where the need for testing exists, but where only a few circuits to be tested are in use. One example of such an application could be a small or rural community having a telephone central office from which only a few special service circuits are provided to customers.
Still another shortcoming of many of these systems is that they require extensive training of personnel to properly operate the central computer-based systems.
One large testing system is utilized by the automated repair service bureau of the Bell System. This bureau includes a mechanized loop testing (MLT) system used to test switched telephone circuits. Another type of loop testing system which is automated is disclosed in U.S. Pat. No. 4,076,970 to Lubarsky, Jr. et al.
Another part of the Bell System circuit maintenance network is the switched access remote test system (SARTS) which utilizes switched maintenance access systems (SMAS) for special service circuits and which also uses remote test systems (RTS).
We are also aware of two test systems provided by Hewlett-Packard. These are the 37100 centralized remote access and test system for voice and data circuits and the 37050S FDM network monitoring system. Both of these are central computer-based systems. The 37100 system utilizes a minicomputer system for maintaining remote control. It also includes access modules and test and measurement units located at the local station for connecting with the circuits to be tested.
Two other systems known to us of particular pertinence because they are disclosed as being for use with relatively small telephone central offices which are to be remotely tested are the Wiltron Model 9900 series centralized maintenance test system and the Design Development, Inc. digital/analog remote test system Model 100R-7. Although these are disclosed to be for smaller applications, they both still utilize centrally located computer systems for controlling the testing and they both require large quantities of on-line memory.
Publications more specifically describing the aforementioned systems and Form PTO-1449 are submitted concurrently with the filing of this application.
In view of the foregoing, there is the need for a less costly test system whereby locations having only a small number of circuits can be accommodated so that these few circuits can be adequately tested to obtain the well-known advantages of faster and cheaper maintenance brought about by having the capability of remote testing. One example of such a location includes end telephone offices having a relatively small number of 2-wire and/or 4-wire special service or private line circuits extending therefrom to the subscribers. Another example of where such a test system is needed within the specific telephone context is at a large subscriber installation where subscriber loop carrier facilities are installed at the subscriber's premises. Again within the telephone context, a preferred embodiment of such a test system should be capable of stand-alone operation so that it does not need to accommodate special or proprietary computer or communications protocols.
To make such a desired system less costly, the system should be designed so that it does not require or use a single central computer to control a number of different units at different locations. However, such a system should still have the ability to comprehensively test the circuits, but without requiring complicated human control or training. Such a system should also be compatible with other mechanized testing systems. While meeting these needs, it is also desirable for such a system to be "smart" enough to "remember" previous transmission or other desired parameters which might need to be varied. This would allow the system to be easily modified and yet the operator would not need to continually re-enter the same parameters every time a test is conducted if such parameters were not changed. Furthermore, it is desirable to have voice communications of the test results provided to the operator over this system, thereby enhancing the ease of using the system while obviating the need for data quality transmission links.